1. Field of the Invention
The present invention relates to the separation of impurities from calcite ore. More particularly, the present invention relates to the flotation of calcite containing rock in the presence of a reagent which separates mineral impurities from calcite.
2. Description of the Prior Art
Calcite is normally separated from limestone rock by the well-known Thompson Weinman process in which the mineral bearing rock is first ground and then the ground material is subjected to flotation. To effect separation of calcite from mineral impurities, the ground ore is subjected to flotation in the presence of xanthate or a tallow amine reagent combination. A particular combination which has been used is a mixture of sodium sec-butyl xanthate (Xanthate 301) and an alcohol type material (MIBC methyl isobutyl carbinol) in amounts of 0.25 to 0.5 pound per ton of calcite ore to float pyrite impurity from the ore. As the type of ore from mine sources has changed with regard to the amount and compositional make-up of the impurities in the ore, problems of brightness and the percentage of insoluble impurities have increased. Consequently, the amounts of micaceous schist and silica have increased in the product calcite to the point where xanthate flotation is undesirable.
In order to overcome this disadvantage, other flotation reagents such as a combination of N-tallow-trimethylenediamine diacetate (Duomac T) and a tertiary amine having one fatty alkyl group and two polyoxyethylene groups attached to nitrogen (Ethomeen 18/60) have been used.
With this combination all of the insoluble impurities can be removed from the calcite rock, i.e., micaceous schist, pyrite and quartz. However, certain disadvantages exist in that the reagents are solid as they are received which consequently requires that the reagents have to be handled, weighed and dissolved in warm water before they can be used in the system. Normally, the reagents are first dissolved to form a 2% or a 4% solution. Also, Duomac-T is very corrosive and tends to promote rust of the iron and steel it contacts. The corrosion of iron and its sensitivity to heat creates a slight loss in the finished color and a browner tint in the calcite pigment. In addition, because Duomac-T is cationic, it causes the fine calcite in the system to disperse which creates difficulties in the settling of the finished products. Further, in a manner not completely understood, the reagent combination apparently adversely affects the grinding and classification of the calcite.
A need therefore, continues to exist for a method by which calcite can be efficiently separated from detrimental mineral impurities without the difficulties of handling and using the prior art surfactants, and without the corrosive properties of the prior art surfactants.